I can think of only two in Maryland. One ford and one low-water bridge (there were once other fords, but those have been closed or been replaced by bridges).
The ford is in Montgomery County, on West Old Baltimore Road in the Boyds area, not especially far from I-270. GSV
hereThe low-water bridge is a toll (!) bridge over the North Branch of the Potomac River, near unincorporated Oldtown in Allegany County. It even has a Web site of its own
here.
The south landing of the bridge is in Green Spring, Hampshire County, West Virginia (but the entire bridge is in Maryland, because the state line is at the "low water mark" on the Virginia (now West Virginia) shore. GSV
here (the toll house can be seen in the distance).
Toll rates are regulated by the Maryland Public Service Commission.